1. Field of the Invention
This invention relates generally to a method and apparatus for locating and positioning a workpiece on a surface and, more particularly, to a locator actuation method and apparatus for locating and positioning a substrate, such as, a multilayer ceramic substrate (MLC), during manufacture and testing thereof.
2. Discussion of the Related Art
Substrate testers are known in the art for performing network integrity tests on substrates, such as multilayer ceramic substrates (MLCs). A substrate refers to a packaging unit that provides an interface between a semiconductor chip (e.g. a very large scale integrated (VLSI) circuit chip) and a higher level packaging unit (e.g., a printed circuit board). A network is generally defined by a set of one or more electrically connected common points on a substrate. Networks are used to distribute electrical signals and voltages externally and/or internally about the substrate in accordance with the requirements of a particular integrated circuit chip. Substrate testers are used during substrate manufacturing to guarantee that there are no process or design created defects (corresponding to opens or shorts) on a particular substrate being tested. Typically, a substrate tester performs a test using a particular contacting scheme. A test matrix scanner is then used to provide an electrical stimulus on each point of the networks contacted by the contacting scheme and then systematically scans the remaining points in the test matrix to guarantee all desired connections exist (opens test) and that there are no unwanted connections (shorts), as the case may be.
In current manufacturing techniques of MLC substrates, there is a need to improve the accuracy and cost structure of substrate locators in an effort to satisfy more stringent manufacturing process requirements. Conventional substrate locators require many moving parts which disadvantageously contribute to tolerance build-ups, inaccuracies, and thus higher manufacturing costs. Conventional substrate locators also use many high precision parts, which are not performance efficient or cost efficient for meeting the current manufacturing requirements. For example, multi-cam drive assemblies are exceedingly costly in terms of their use in the manufacturing process.
Current state of the art substrate locators include a number of moving parts, which may include parts such as precision cam slots, cam followers, gears, etc.. The moving parts contribute to a build up of tolerances. This build up of tolerances prevents a precise and absolute locating and positioning by the locator with respect to a centering of the substrate parts over or under a workstation, wherein the workstation requires extreme positioning accuracy and repeatability. The workstation may also include a high speed substrate tester (HSST) which has traditionally been characteristically large and slow.
Features on MLC substrates are very small and in close proximity to one another. For example, any one particular MLC substrate may include more than one thousand pin or pad connections in an area on the order of one-quarter square inch of space, as can been realized in the current state of art for MLC substrates. It is thus very critical to align the substrate parts in a repeatable manner, for example, with respect to a testing and a placement of test contacts, or other processing and manufacturing options, such as chip placement, discrete wiring, etc.
U.S. Pat. No. 4,436,385, issued Mar. 13, 1984 and entitled "Specimen Holder for Inverted Microscopes" discloses a specimen holder having a wide range of capability for replaceably accepting and holding any one of a variety of sizes and shapes of specimens. In one embodiment, the specimen holder includes a release and clamp mechanism for one-handed operation. A series of interconnected mechanical links are disposed between a first plate and a second plate. The interconnected links pivot with respect to each other at their respective interconnections. Furthermore, one of the interconnected links includes a pin and slot connection to one of the plates, which further pivots about a pivot point for moving the plates towards each other or away from one another via the multiple interconnected links. However, a given amount of movement in one direction by the pin and slot connected linkage does not produce a corresponding same amount of movement of the corresponding connected plate when the pin and slot connected linkage is moved the same given amount in an opposite direction. Accurate determinable positioning is thus not attainable. This is because the specimen holder suffers from an undesirable buildup of tolerances as a result of the multiple interconnected linkages and the slot and pin connection. Non-uniform plate movement further results in a different centerline location for each successive clamped specimen. In addition, not all of the components of the specimen holder are in tension during a clamping operation, thus the specimen being clamped is subject to a non-uniform clamping force and possible mis-positioning.
In addition, in today's MLC substrate manufacturing environment, a wide variety of substrate sizes are manufactured. For testing of the various sized substrates, the substrate tester must undergo a product changeover to accommodate a substrate of a different size from that which it was previously set up for. This has lead to the use of expensive multiple hardware for making a product changeover, further resulting in a lengthy and inefficient changeover process.
It would thus be desirable to provide a locator which can accurately locate and repeatably position MLC substrates with respect to a centerline location during a manufacturing process, and furthermore, reduce the manufacturing costs of producing the same.
It would further be desirable to provide a product tester having capability for handling a wide variety of substrate sizes in a manner which enables product changeover to be economical, relatively quick and efficient.